Search Documents

By N. L. Weiss

General The crushing of run-of-mine hard rock ores is the province of jaws and gyratory primary crushers described in the two preceding chapters of this section. While it is now seldom difficult to make a choice between the two to suit a specific set of circumstances, the governing factors merit a review, and that is the purpose of this chapter. For every size of feed there is a crusher of either type that can handle it, and it is only when the desired crushing rate in toss per hour is considered together with the rock size that the preference for one type over the other is truly significant. When Taggart completed his Handbook of Mineral Dressing there were already in opera-

Jan 1, 1985

By W. Lawrence Austin

At the Troy meeting of the Institute, in October, 1883, I presented a paper entitled "Smelting Notes from Chihuahua, Mexico,"" in which was briefly described a cupellation-hearth, commonly met with in the northern part of Mexico, called in the vernacular un vaso. Since writing the paper I have had occasion to construct a hearth of this description for myself, using it, in conjunction with a waterjacket, for the reduction of a very refractory ore in the form of concentrates ; and I now avail myself of this opportunity to qualify some of the statements made in the paper referred to. At the same time I wish to present some sketches which will enable anyone to run up a similar furnace within three days, should occasion demand

Jan 1, 1885

By Y. J. Wang

This paper describes a procedure for solving the generalized system of n network equations in n unknowns considering the following ventilation variables and parameters: (a) air quantities, (b) pressure losses or gains caused by the control devices (i.e., fans or regulators), (c) resistance factors, (d) natural ventilation pressure, and (e) fan pressures (as a function of air quantities). The air quantities and pressure losses for all branches in the network are grouped into dependent and independent variables. The branches with an independent quantity are contained in a chord set, and the branches with a dependent pressure loss are contained in a chord set. In addition to the problem formulation, the solution procedure, applying the Newton method, is discussed and illustrated with a numerical example.

Jan 1, 1989

By M. Y. Xia

In this paper, based on the Theological tests of the interface between clay and concrete, an interface Theological model is proposed and is used in the finite element analysis which takes soil as viscoelastic mass and Theological effect of the interface between diaphram wall and ground into consideration. Its results are compared with those without an interface element, without considering the relative creep displacement. Close attention is paid to the variation of wall with time under the condition of various interface shear stiffness and viscous sliding coefficient, and their effects on the wall bending moment are primarily verified in the paper. The change of wall bending moment with time, trench heave and wall displacement in different excavation depth, bracing position, parameters for soil are also studied.

Jan 1, 2010

By Christopher Haycocks, J. Richard Lucas

The growth of computer and ground control technology in recent years, combined with an urgent demand for low-cost fossil fuels and mineral resources, has set the stage for full-scale utilization of computers in mine planning. Steeply rising production costs and the need to preserve the environment are placing great demands on engineers to improve their mining efficiencies, which can best be accomplished by applying the full capabilities of the computer. Pressure to develop and perfect programs with an immediate potential for improving mine design, reducing mining costs and extending the viable coal reserves of the country has already come to bear in the form of exploding energy requirements, environmental considerations and the visible limitations of other energy sources.

Jan 4, 1973

By R. Butar-Butar, J. Mosher, G. Banini, J. Hollow, A. Villanueva

The effect of High Pressure Grinding Rolls (HPGR), as a preceding stage to a conventional ball mill circuit at PT Freeport Indonesia’s C1/C2 concentrators, has been studied in terms of downstream grinding efficiency and circuit performance. When milling the product from the HPGR, mill capacity increased by 21% for the same product grind size, when compared to processing similar ore from a conventional crushing circuit. This achievement is a result of several reasons, among them: reduction in feed size (F80), fines generation beyond the proportional reduction in F80, reduction in ore hardness induced by HPGR comminution mechanism, optimization of the recycle system of the HPGR and ball string optimization in the ball mill circuit given the new feed to the mill.

Jan 1, 2012

By Lawrence F. Schubert

Instrumentation is not a stranger to the minerals processing industry. In fact, very few plants now exist that haven't to one extent or another adapted operations to instrumentation. But with the rapid growth of such controls has come the need for effective departments composed of men trained to maintain and repair the instruments; here is where many firms fall short. The importance of the role an instrument department should play is underscored by the omnipotent effects which instruments often exert over an operation. Reserve Mining Co. is an example: while instrumentation at this taconite plant represents approximately 2% of the process equipment cost, a breakdown of instruments may result in the ineffective use (or complete shut-down) of the other 98% of plant investment.

Jan 7, 1966

By Alan P. Cook

Methane levels have been measured around continuous miners and compared with computer simulations of methane flow. A multi-channel data logger, reading continuously from six methanometers, has shown methane levels to vary at different positions around a continuous miner, with the cutting drum and the immediate face area not necessarily recording the highest concentrations. Methane levels in the driver's cabin are generally low compared with the return side. Computer simulations, using computational fluid dynamics, have been supported by the measured data, and have shown that methane behaviour within the first few metres of the face varies considerably for different bord and pillar development stages. Methane is diluted rapidly to acceptable levels, but the distance required for this is extended when ventilation flow to the face is restricted.

Jan 1, 1995

By Michael E. Mcllwain, Lee O. Nelson, Robert D. Rogers, James H. Wolfram

Examination of the economics and environmental consequences associated with phosphate fertilizer production documents the necessity for development of innovative production technologies. Evidence of phosphate ore's susceptibility to microbial alteration indicates that it will be an ideal candidate for industrial-scale bioseparation. There are at least two applications for the biosolu- bilization technology: (1) an industrial-scale bio- process similar to the presently used wet acid process and (2) production of small prills (bio- bead) containing unprocessed rock phosphate and the biological ingredients necessary to promote phosphate solubilization. At the present stage of development, the biobead technology is the preferred application. It is an energy-efficient "green" technology that will dramatically reduce the amount of solid waste and air emissions produced by the phosphate industry.

Jan 1, 1999

I have attended these meetings, every year, since 1926 and have served on both the Pittsburgh and the National Executive Committees, so that I am fully aware - of the ruling of this organization regarding, "No Papers by Vendors". Since I am now classified as a VENDOR, I wish to express my sincere appreciation for the invitation to formally discuss these very interesting papers --all of which herald the coming of an entirely new era in the manufacture of quality steels. I also appreciate the references by Mr. Mosser and Dr. Swinkels to my first paper on the oxygen probe which was presented at the meeting of this group, here in Chicago, in 1966 and was subsequently published in the NOH Proceedings of that year. (1)

Jan 1, 1972

By H. T. Lundberg, J. H. Ratcliffe

In airborne gravity surveys effects of acceleration and irregular movements of the aircraft must be balanced out or overcome. The gradient of vertical gravity is recorded, therefore, by using two masses instead of one. As the amplitude variations are infinitesimal and difficult to measure accurately, at present it is enough to determine whether variation of gradient during flight is positive or negative. The positive portions of the pattern can then be indicated and contoured. Even with these simplifications, the source of energy must be exceptionally stable. General Principles: In the conventional gravi-meter the weight of a standard mass is determined at a number of selected points within the survey area. In most systems weight is determined by comparing the gravity pull with extension or torque

Jan 1, 1960

This paper discusses the type of scaling operations presently in use in underground mines. It defines a scaling factor that is expressed as the area necessary to scale to extract 1 t (1.1 st) of ore. The problems associated with conventional scaling methods are discussed as well as recent developments in mechanized hand-held scaling de- vices and methods of loose detection. The elements of the scaling process are further analyzed. The conception and design of a mechanized scaling device, developed at Universite' Laval is also described. The results of field tests conducted in Quebec hard rock mines are presented. The experimental findings show that the mechanized hand-held scaling device shows potential in improving the productivity and safety of underground mining operations.

Jan 1, 1996

By R. Corriveaau

This paper is about a horizontally curved conveyor, which carries 6,050 stph of limestone over land from a new quarry to the owner's plant. The conveyor is 5,012 ft long with a horizontal curve radius of5,OOOft Site conditions made a curved conveyor design the most optimal and economic solution. Using our unique custom conveyor calculation program, TKRI was able to accurately model and design the conveyor to properly track the belt and prevent any spillage through the horizontal curve radius. A data monitoring system was installed that allows monitoring of the conveyor both locally and remotely. The remote monitoring allows TKRI to contact the owner for preventive maintenance. Preventive maintenance can reduce the conveyor downtime during normal operating hours.

Jan 1, 2004

By Lawrence Burkhart, S. B. Joo

A hemispherical, constant volume drop with forced internal circulation was considered as a model approximating a real drop at a similar stage of formation Axially symmetric steady flow within a drop contaminated by surfactants was described by solving the full Navier-Stokes equations written in terms of a meridian plane stream function Rotational flow occurred inside the drop above a computed Reynolds number of 5.8, and the change in interfacial flow caused by imposing a surface-tension gradient at the surface had a significant effect on the internal flow Although the work is quite fundamental in nature, the rotational flow described in the paper is responsible for much of the bulk transport of solute to the interface in hydrometallurgical processes such as solvent extraction.

Jan 1, 1981

By Mark W. Springett

The examination of relatively well behaved distributions subject to truncation by a cutoff grade in the mine clearly demonstrates that a bias is inevitably introduced when the selection is based on the results of samples which are subject to even the most idealised error distribution. The idealised error used in this paper is assumed to be normally distributed with a mean of zero and is thus unbiased. The bias introduced can be minimised but it cannot be eradicated. A better understanding of the bias can lead to improved procedures for mine sampling, sample preparation, assaying and estimation of selection units which will not only reduce the discrepancy but more significantly will increase the efficiency of mining selection and hence profitability.

Jan 1, 1989

By J. K. Gerlach, E. D. Gock, S. K. Ghosh

Previous experience in leaching chalcopyrite with dilute sulfuric acid has generally resulted in rather poor extraction. However, the reaction rate of the leaching process can be significantly improved by an increase of the crystal lattice defects of the chalcopyrite. It was found that subjecting chalcopyrite to a milling action involving a strong impact, permits 99 percent of the copper to be extracted in a subsequent single leaching stage with at least stoichiometric quantities of sulfuric acid in the presence of oxygen at 100°C. Simultaneously, about 80 to 85 percent of the sulfide sulfur content is converted to elemental sulfur. The dependence of the reaction rate of chalcopyrite on the pretreatment, temperature, oxygen pressure and acid content will be discussed.

Jan 1, 1973

By P. Coleman, J. C. Kerkering, S. Iverson

Fault tree analysis is a systematic safety analysis tool that proceeds deductively from the occurrence of an undesired event (accident) to the identification of the root causes of that event. One recurring mine safety problem—a dozer falling into a void over a drawpoint on a coal surge pile—was analyzed using available, inexpensive fault tree programs on a personal computer. The analysis identified basic and intermediate events that led to the burial of the dozer and graphically depicted the interrelationship between these various subordinate events as well as the various chain of events leading up to the primary event. A sensitivity analysis on these probabilities showed which events had the greatest influence on dozer burial in a coal surge pile.

By H. William Ahrenholz

Many technical meetings were attended by mining people during the past year in which rock mechanics was either the main subject for discussion or was a prominent part of the program. Several universities continued to offer short courses in the applications of rock mechanics for practicing mining engineers. At the beginning of the year, the AIME Committee on Rock Mechanics achieved standing-committee status. It is to assume responsibility for coordinating all AIME activities in this area. Eleven professional societies are now participating in a newly formed Intersociety Committee for Rock Mechanics. AIME and its constituent societies has three representatives. Delegates from the Intersociety Committee will serve on the U.S. National Committee for Rock Mechanics which is being formed by the national Academy of Sciences.

Jan 2, 1967

By Derek G. Cieplinski

Regenerative conveyors with complex conveyor profiles place unusually stringent demands on the starting drive control. Depending on the nature of the conveyor loading, the drive must either provide a positive driving force to overcome conveyor friction and gravitational forces if the belt is empty or the inclined sections are loaded, or it must provide a retarding force to resist the gravitational load of decline sections to control the acceleration rate. This paper discusses the requirements of regenerative conveyors, reviews the working principals of fluid couplings, and examines their interaction by means of a case study of a 1700 m long regenerative conveyor utilizing a fluid coupling with a proportional brake control to provide controlled starting and stopping under all load conditions.

Jan 1, 1993

By Helen L. Cannon

BOTANICAL methods of prospecting for metalliferous ores are based on the premise that deposits at depth may be reflected chemically in surface vegetation. For the past several years, on behalf of the Atomic Energy Commission, the U. S. Geological Survey has investigated on the Colorado Plateau the application of botanical methods to uranium prospecting. Results suggest that orebodies may be found under a considerable cover of barren sandstone through the absorption of uranium and associated trace elements by plants growing at the ground surface. Plant physiologists have demonstrated that uranium is a necessary nutrient for plant growth and therefore is present in all plants.' The amount present is small but measurable. The absorption of uranium by plants growing over ore deposits forms

Jan 1, 1955